A Case of Hypercalcemia and Acute Kidney Injury Caused by Adrenal Insufficiency.

Hypercalcemia is a common electrolyte disturbance, most frequently caused by hyperparathyroidism or malignancy, though it can also arise from adrenal insufficiency, creating diagnostic challenges. We present a case of a 78-year-old male patient with stage 3b chronic kidney disease due to immunoglobulin A nephropathy who exhibited altered mental status following dehydration caused by a five-day episode of diarrhea. The patient presented with hypercalcemia and acute kidney injury. His history of adrenal insufficiency had been managed with glucocorticoid replacement. Dehydration and inability to take oral medications led to exacerbation of adrenal insufficiency, worsening his hypercalcemia. Routine causes of hypercalcemia, such as hyperparathyroidism and malignancy, were ruled out. Treatment with intravenous prednisolone and fluid replacement gradually improved serum calcium and mental status, with normalization by the seventh hospital day. This case highlights the importance of timely glucocorticoid therapy in managing adrenal insufficiency-related hypercalcemia and the complex mechanisms involved, including decreased glomerular filtration rate and increased calcium reabsorption.